Heat and humidity can be lethal for your players — here's what to know

(Because a record-setting heat wave is hitting the nation, and in some areas youth soccer is returning in various phases, we republish this article that first appeared in Soccer America in Augustof 2018. For U.S. Soccer’s return to play recommendations — to be “implemented only if and when local regulations deem it safe” — go HERE.) * * * * * * * * * *

It can be OK to practice in 100-degree weather, or it could be dangerous. It depends on the humidity factor.

So impactful is humiditythat, for example, 86-degree weather can be lethal if humidity is extremely high.

“Humidity is probably the key factor that could be the most difficult on the body with regards toexercise, because with the humidity, your body’s ability to dissipate heat is stunted,” says Dr. George Chiampas, U.S. Soccer’s Chief Medical Officer. “Youcan’t sweat it off because the environment outside of you is hotter than yourself.”

Therefore, coaches must figure out the Wet Bulb Globe Temperature (WBGT) — when decidingwhether to cancel or delay training, or games.

If WBGT sounds complicated, it’s made comprehensible by U.S. Soccer’s “HeatGuidelines,” part of its Recognize to Recover Program overseen by Chiampas.

“WBGT is becoming a more and more a common term in youth sports and in sports in general,” he says.

The R2R “Heat Guidelines” provide a graph to estimate WBGT (for which there are also apps, such as WeatherFX, and WBGT monitors). Also included in the Guidelines is a list of indicators of heat-illness and heat stroke (which can be life-threatening), management and recoveryinformation, acclimatization procedure, and work-to-rest ratio formulas.

Emphasized also is access to cooling and hydration resources.

“We’re understanding more and more inregards to heat and acclimatization,” Chiampas said. “We also see that there have been extremes in temperatures over the last 10 years.”

The Guidelines break the nation intothree geographic parameters based on how acclimated players are to heat, because, “Players who are playing in the South are more acclimated to warmer weather compared to players who are playing theNorth,” Chiampas says.

The main emphasis of the Guidelines is playersafety, but they also serve to optimize performance.

“If as coach, you start learning more about exercising in the heat, this is gives you some insight into the importance of it and thatit is a factor in the ability of your players to play at a high level,” Chiampas says. “It also gives you some action items of things that you can do, such as adjust your work-rest ratio.But I think most importantly it’s providing coaches, parents and players, as well as referees, a user-friendly process to implement a very important safety component.”

• The U.S. Soccer Federation R2R Guidelines aremandated for Development Academy clubs, serve as guidelines for USSF members, and meant as a resource for American soccer outside its membership.

• For Heat Guidelines, go HERE.

• The R2R home page is HERE.